During the process of assembling a structure, it is typically desirable to inspect the structure to determine whether certain features are located within design tolerances. For example, many structures are assembled using mechanical fasteners such as bolts or screws to attach mating parts to the structure. The mechanical fasteners may be installed in holes that are formed in the structure at a desired location. In order to provide sufficient strength to handle stresses transmitted to the structure by the mechanical fasteners, the holes are preferably located at a minimum distance from the edge of the structure.
Current methods of inspecting an assembly for the location of holes and other features include the use of hard tooling. Such hard tooling may be mounted to the assembly or to a fixture for holding the assembly in place. The hard tooling may include markings indicating the desired location of the features such as holes that may be formed in the assembly to allow the attachment of mating parts. Unfortunately, hard tooling must typically be fabricated with relatively tight tolerances which increases the overall cost of manufacturing the assembly. In addition, hard tooling may require manual engagement of the tooling to the assembly which may interrupt manufacturing operations. Furthermore, such hard tooling may require the use of skilled labor for inspecting the assembly in a time-consuming process of manually determining whether features in the assembly are located within design tolerances.
Another method of inspecting an assembly for the location of features includes the use of a coordinate measurement machine (CMM). A CMM may include a touch probe that may be mounted to a moveable arm or a gantry. The touch probe may be computer-controlled or manually-controlled to guide the touch probe to different inspection locations of the assembly. At each inspection location, the touch probe may be placed in contact with one or more features such as a hole in the assembly to determine the coordinates (i.e., x, y, z) of the features relative to a reference point on the assembly. The measured coordinates may be compared to a desired location of the feature to determine whether the feature location is within design tolerances. Unfortunately, CMMs are typically relatively expensive and may require the use of skilled labor for operating a CMM. A further drawback associated with CMMs is that the moveable arm or gantry of the CMM may provide limited access to certain areas of the assembly. Even further, production of the assembly may be halted when the CMM is in use resulting in a negative impact on the production schedule.
As can be seen, there exists a need in the art for an automated system and method for accurately measuring the size and location of the features of an article. Furthermore, there exists a need in the art for a system and method for non-invasively measuring the features of an article without suspending manufacturing operations. In addition, there exists a need in the art for a system and method for measuring the features of an article that is of low cost and which is adaptable for inspecting a wide variety of article configurations.